A projector is used for projecting an image onto a projection plane such as a screen. For using such a projector, a projector color correcting method has been known for correcting an image on the projection plane for colors such that the colors precisely match colors recorded in image data.
For example, JP-A-2001-320725 discloses a technique for an environment adaptive image processing method for correcting colors projected by a projector. This technique corrects images for colors in accordance with visual environments. Then, this technique includes a step of capturing a visual environment, a step of converting the captured visual environment into coordinate values in a predetermined color space, a step of correcting input/output data for display based on coordinate values in a predetermined color space of a predetermined color in a predetermined reference environment correcting, the converted coordinate values, and coordinate values which form a complementary color pair with the converted coordinate values, and a step of displaying an image based on the corrected input/output data.
In this color correcting method, input/output characteristic data for display, used by image display means, is corrected on the basis of coordinate values which reflect projector environment information and the coordinate values which form a complementary color pair, thereby realizing the reproduction of colors which are adapted to an environment during display. A specific color reproducing method involves capturing color information (RGB, XYZ or the like) available from the projection plane of a white image using a color sensor, and mapping color information on the captured white image to an original CIELAB color space at a previously set standard white. In this event, if the standard white does not reside on an L-axis, a bound vector is calculated from the L-axis on an ab plane of the white, and a color corresponding to the position of the opposite vector from the L-axis, i.e., a complementary color, is found and supplied as a corrected color. Actually, this processing is performed on a plurality of halftone achromatic colors other than the whitecolor, and this is realized in a form of storage in gamma correction LUT.
Such a conventional projector color correcting method is premised on the projection plane in a uniform color, which is a factor that affects color reproduction of a projector. Therefore, a more precise color correction cannot be accomplished if the projection plane is not uniform in color. The reason for that lies in that the conventional color correcting method, though acquiring color information on the projection plane, fails to acquire detailed color information corresponding to the pixel level of a projected image, and can therefore perform color correction processing only for one type of color corresponding to the averaged color on the projection plane.
In addition, the conventional projector color correcting method is premised on the absence of patterns on the projection plane, which is a factor that affects the color reproduction of a projector. Therefore, a more precise color correction cannot be accomplished if patterns exists in the projection plane. The reason for that lies in that the conventional color correcting method, though acquiring color information on the projection plane, fails to acquire detailed color information corresponding to the pixel level of a projected image, and can therefore perform color correction processing only for one type of color corresponding to the averaged color on the projection plane.
Further, the conventional projector color correcting method is premise on environmental light uniformly impinging on the projection plane, which is a factor that affects the color reproduction of the projector. Therefore, a more precise color correction cannot be accomplished if the environmental light does not uniformly impinge on the projection plane. The reason for that lies in that the conventional color correcting method, though acquiring color information on environmental light on the projection plane, fails to acquire detailed color information corresponding to the pixel level of a projected image, and can therefore perform color correction processing only for one type of color corresponding to averaged environmental light on the projection plane.
A desire exists for techniques which are capable of improving the accuracy of color reproduction of a projector. A desire exists for techniques which are capable of realizing stable color reproduction even in a situation where the projection plane of a projector is not uniform in color. A desire exists for techniques which are capable of realizing stable color reproduction even in a situation where environmental light does not uniformly impinge on the projection plane of a projector.
As a related technique, JP-A-2000-31670 discloses a technique for a color uniformity correcting method. This technique is a color uniformity correcting method for displayed colors on an optical display plane on which a displayed color image is generated by the image generator of a display device. The optical display plane on which a reference color image is displayed by reference color image data applied to the image generator is partitioned into a plurality of triangular areas. Color coordinates are measured at reference pixels positioned at three apices of the respective triangular areas. A luminance correction amount is determined at the reference pixel simultaneously. The luminance correction amount is found according to a predetermined function at each of the pixels within the respective triangular areas based on the luminance correction amounts at the three reference pixels in the respective triangular areas. Color image data corresponding to each pixel in the respective triangular areas, applied to the image generator, is corrected in accordance with the luminance correction amount.
This technique is intended to appropriately determine a proper amount for correcting lack of uniformity in colors on the display screen in order to carry out appropriate corrections of the details on the display screen.
JP-A-11-313346 discloses a technique for a projected video image testing apparatus. This technique is configured to measure an absolute optical amount of a projected video image based on a comparison of an optical amount by an optical sensor mounted on a screen with an optical amount of a portion corresponding to the position of the optical sensor in the imaged data of the projected video image on the screen to generate the result of the measurement.
JP-A-2002-41016 discloses a technique for an environment adaptive image display system. The image display system based on this technique is an image display system for correcting and displaying an image based on environment information indicative of the visual environment in a displayed area of the image. The system includes means for storing, and correcting means for correcting. The means for storing stores brightness correction information for correcting the image for brightness based on the environment information, and color correction information for correcting the image for colors based on the environment information. The correcting means for correcting corrects image information for displaying on image based on the brightness correction information and the color correction information.
JP-A-2002-125125 discloses a technique for an environment adaptive image display system. The image display system based on this technique is an image display system for correcting and displaying an image based on environment information indicative of the visual environment in a displayed area of the image. The system includes correcting means for correcting display input/output characteristic data for use by means for displaying the image to increase the output, at least in a low halftone band, based on the environment information when there is the influence of environment light.
JP-A-2003-50572 discloses a technique for an image display system. The image display system based on this technique is an image display system for correcting an image for halftone in accordance with an environment. The system includes image displaying means, environment capturing means, and halftone correcting means. The image displaying means displays a calibration image. The environment capturing means captures an environment in which the image displaying means is used to generate use environment information indicative of the use environment. The halftone correcting means makes the halftone correction based on the use environment information. The image displaying means displays calibration images in the same color but at two different halftone levels, and displays an image which has been corrected for halftone. The environment capturing means generates two types of use environment information in a state where the calibration image at each halftone level is displayed. The halftone correcting means makes the halftone correction based on the difference between two types of ideal environment information indicative of environments which are captured when the calibration images at two halftone levels are displayed under an ideal environment, and based on the difference between the two types of use environment information.